1) Right click the affiliation you want and select "Properties". Double click the Address (URL) so that the entire address is highlighted.
2) Right click the highlighted address, COPY.
3) Go to your User CP.
4) Go to Edit Signature
5) In the box at the bottom of the page, select the IMAGE button. (yellow box with a mountain and a sun next to the quote and hyperlink button)
6) PASTE the address into the popup menu.
7) You're DONE
8) repeat 1-7 for more, or any, sigs.